# [Tutor] Tutor Digest, Vol 48, Issue 2

William Kilmartin williamakilmartin at yahoo.com
Sat Feb 2 22:07:47 CET 2008

```Thanks!

I'll get to work!

"Microsoft isn't evil, they just make really crappy operating systems."
-Linus Torvalds

tutor-request at python.org wrote:
> Send Tutor mailing list submissions to
> 	tutor at python.org
>
> To subscribe or unsubscribe via the World Wide Web, visit
> 	http://mail.python.org/mailman/listinfo/tutor
> or, via email, send a message with subject or body 'help' to
> 	tutor-request at python.org
>
> You can reach the person managing the list at
> 	tutor-owner at python.org
>
> than "Re: Contents of Tutor digest..."
>
>
> Today's Topics:
>
>    1. matrix-vector multiplication errors (Dinesh B Vadhia)
>    2. Where to start? (William Kilmartin)
>    3. Re: Where to start? (Alan Gauld)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 1 Feb 2008 14:13:00 -0800
> Subject: [Tutor] matrix-vector multiplication errors
> To: <tutor at python.org>
> Message-ID: <BAY109-DAV19D95746E8E1D1C1DCC431A3300 at phx.gbl>
> Content-Type: text/plain; charset="iso-8859-1"
>
> I've posted this on the Scipy forum but maybe there are answers on Tutor too.  I'm performing a standard Scipy matrix* vector multiplication, b=Ax , (but not using the sparse module) with different sizes of A as follows:
>
>
> Assuming 8 bytes per float, then:
> 1. matrix A with M=10,000 and N=15,000 is of approximate size: 1.2Gb
> 2. matrix A with M=10,000 and N=5,000 is of approximate size: 390Mb
> 3. matrix A with M=10,000 and N=1,000 is of approximate size: 78Mb
>
> The Python/Scipy matrix initialization statements are:
>
>> A = scipy.asmatrix(scipy.empty((I,J), dtype=int))
>> x = scipy.asmatrix(scipy.empty((J,1), dtype=float))
>> b = scipy.asmatrix(scipy.empty((I,1), dtype=float))
>>
>
> I'm using a Windows XP SP2 PC with 2Gb RAM.
>
> Both matrices 1. and 2. fail with INDeterminate values in b.  Matrix 3. works perfectly.  As I have 2Gb of RAM why are matrices 1. and 2. failing?
>
> The odd thing is that Python doesn't return any error messages with 1. and 2. but we know the results are garbage (literally!)
>
> Cheers!
>
> Dinesh
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL: http://mail.python.org/pipermail/tutor/attachments/20080201/5c3abb34/attachment-0001.htm
>
> ------------------------------
>
> Message: 2
> Date: Fri, 01 Feb 2008 20:52:39 -0800
> From: William Kilmartin <williamakilmartin at yahoo.com>
> Subject: [Tutor] Where to start?
> To: tutor at python.org
> Message-ID: <47A3F717.90708 at yahoo.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Here's what I'm trying to accomplish;
>
> I track statistics at work.  E.g. calls out, \$ collected etc..
>
> The graph has a rough guess of highest possible at the top and the
> lowest number in the past 3 months at the bottom.
>
> It's a simple line graph, week after week.
>
> I need to be able to add names of various statistics.  I.e. calls out,
> money collected, proposals sent etc..
>
> It then needs to create the graph, store the names, be able to take the
> week's numbers and store them along with being able to print.  The
> highest and lowest points also need to also be inputed and changed if
> needed.
>
> Ideally this would be a GUI driven app for the sake of simplicity.
>
> What I'm looking for is advice on where to start, a middle ground and an
> end.  I'm new to Python and programming and took this as the 1st thing
> I'd to create.
>
> I've been studying for a bit now and knowing where I'm going would be